대 한 방 사 선 의 학 회 지 1992 ; 28 (4) : 601 ""608 Journal of Korean Radiological Society, July, 1992

CT Characterization of Bile Duct Dilatation: Differential Diagnosis of Obstructive Jaundice

Jae Hoon Lim , M.D. , Yup Yoon, M.D. , Young Tae Ko, M.D. , Dong Ho Lee, M.D. , Ik Yang, M.D.

Department o[ Diagnostic Radiology Kyung Hee University Hospital

- Abstract-

Each Disease affecting the bile ducts tends to produce characteristic pattern of biliary dilatation: recur­

rent pyogenic cholangitis causes dilatation and straightening of the larger(central) intrahepatic ducts ; clonor­

chiasis causes dilatation of the smaller (peripheral) intrahepatic ducts; and carcinoma along the extrahepatic

ducts causes (proportional) dilatation and tortuosity of both larger and smaller intrahepatic ducts. To evaluate

the speci디city of the pattern and morphology of the dilated biliary tree on CT scans (CT characterization)

three independent radiologists who were unfamiliar with the cases were asked to classify 62 CT scans in

patients with obstructive jaundice .

The case population consisted of 14 cases with recurrent pyogenic cholangitis , 18 cases with clonorchiasis

and 30 cases with carcinoma along the extrahepatic ducts. which were intermixed randomly. Classification

was made only on the basis ofCT characterization: those scans showing primary lesions , i.t., stone , aggregate

of flukes. or tumor mass were excluded or masked . All the scans of every case showing the extrahepatic bile

duct were masked.

Radiologists correctly classified 54 of the 62 cases (87%): ten of the 14 patients with recurrent pyogenic

cholangitis(71 %). 17 of the 18 patients with clonorchiasis(94%) and 27 of the 30 patients with carcinoma

along the extrahepatic bile ducts(90%).

We believe that CT characterization ofbile duct dilatation is useful in the differential diagnosis of obstruc­

tive jaundice. especially when a primary pathologic lesion is not depicted in CT scans.

Index Words: Bile ducts , CT 766.1211

Bile ducts , calculi 766.2896

Bile ducts. neoplasms 766.321

Bile ducts. clonorchiasis 766.2085

Cholangitis 766.202

INTRODUCTION

Sonography and CT are the two most non­

invasive diagnostic armamentarium in the dif­

ferential diagnosis of obstructive jaundice. Dif­

ferentiation of obstructive jaundice from

non-obstructive jaundice is possible over 98% of

the time by recognizing the dilated bile ducts.

However , accuracy of identification of the causes

of bile duct obstruction is 71-88% by

sonography( l, 2) and 63-70% by CT(2. 3) . The

primary lesion is often elusive. and ultrasonogram.

CT scan , or cholangiogram just reveals biliary

dilatation: in these cases, however , diagnosis could

be suggested on the basis of pattern of dilatation ,

that is distribution and shape ofthe dilated biliary

tree. and further appropriate procedure could be

tailored.

Authors attempted to assess the diagnostic

value of CT characterization of the biliary tree in

the differential diagnosis of the three most com­

mon biliary tract diseases , namely recurrent

이 논문은 1992년 2월 10일 접수하여 1992년 4월 28일에 채택되었음.

Rece ived r ebruary 10. Accepted April 28 ‘ 1992

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Journal of Korean Radiological Society 1992 ; 28(4):601""608

pyogenic cholangitis(RPCJ , clonorchiasis, and car- CT scans were obtained with a CT/T 9800

cinoma along the bile ducts . Quick scanner (GE Medical Systems ,Milwaukee)

MATERIALS AND METHODS

The study population consisted of 14 patients

with RPC , 18 patients with clonorchiasis, and 30

patients with carcinoma along the bile ducts (ten

patients with cholangiocarcinoma of the ex­

trahepatic ducts, 13 patients with pancreatic head

carcinoma, and seven patients with carcinoma of

the ampulla of Vater). These were consecutive

cases during the period from April1988 to March

1991 except following cases; (1) those cases show­

ing direct evidence of a disease on CT , namely

stones in RPC , aggregate of f1ukes in clonorchiasis

or mass in carcinoma(when the direct evidence

was only in the extrahepatic ducts , those cases

were included , because every CT slice of all the

cases showing extrahepatic ducts was masked): (2)

those cases having two kinds of diseases , such as

clonorchiasis and cholangiocarcinoma, or clonor­

chiasis and RPC; (3) those cases that underwent

interventional procedure before CT scanning since

a catheter in the bile ducts implies malignant

biliary obstruction in our hospital: (4) those cases

in which the diagnosis was not confirmed. There

was no case of sclerosing cholangitis or Caroli

disease during the same period. There were four

cases of choledochal cyst but these were exclud­

ed since the extrahepatic dilatation was evident

and quite characteristic for the disease.

Among the 14 patients with RPC , the diagnosis

was based on the surgical findings and cultures

in ten patients, and clinical as well as endoscopic

retrograde cholangiographic findings in the other

four patients. Clonorchiasis was diagnosed on the

basis of demonstration of ova of Clonorchis sinen­

sis in stool in 14 patients, and skin test (veronal­

buffered saline extract of adult worms of Clonor­

chis sinensis , 1; 10 ,000 dilution) in four patients.

In cancer, 19 cases were diagnosed surgically an­

d/or pathologically , and the remaining 11 cases

were diagnosed on the basis of clinical and

cholangiographic findings

in 48 patients and other commercially available

third generation scanners in the remaining 14 pa-

tients . Some CT scans were obtained both before

and after contrast enhancement but we reviewed

only the postcontrast scans. Postcontrast scann­

ing was performed after bolus injection of 150 ml

of 60% iothalamate meglumine (iodine content,

28% ), (Conray; Mallinckrodt Institute Canada,

Quebec, Canada). Contiguous scans with l-cm col­

limation (n=51 ), or 5-mm collimation with 2-mm

interslice gap (n = 11) were obtained covering the

entire liver and pancreas.

The CT scans were mixed randomly. Every CT

slice of all the cases showing extrahepatic bile

ducts were omitted or masked so that the

radiologists should think there might be a lesion

in the extrahepatic bile duct or pancreas in all the

cases included in this study.

Three radiologists (two gastrointestinal

radiologists [YTK. DHL) and one chest radiologist

[YY) who were unfam i1iar with the cases and blind­

ed to the clinical information were asked to review

the CT scans at the same session but answer in­

dependently. Before the test cases were reviewed,

there was a brief introduction session explaining

the proposed criteria using typical cases of each

disease . Radiologists were not informed about the

number of cases included for each disease. Each

radiologist was asked to diagnose one ou t of three

diseases.

The radiologist were asked to diagnose RPC

when the larger intrahepatic bile ducts (central

one-halffrom the p아ta hepatis) are predominantly

dilated with no dilatation of the smaller bile ducts

(“central" dilatation , Fig. 1, 2) in association with

abrupt tapering and straightening; clonorchiasis

when the small or medium sized intrahepatic bile

ducts (peripheral one-halffrom the porta hepatis ,

namely tertiary , quaternary and more peripheral

division) are predominantly dilated (“ peripheral' .

dilatation , Fig. 3); carcinoma when the entire

biliary tree is dilated proportionally (more dilata­

tion in central and less in peripheral) with some

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Fig. 1. Central dilatation in a 66-year-old man with recurrent pyogenic cholangitis. CT scan shows dilata­tion of the large intr와1epatic ducts including the right and left hepatic ducts and segmental ducts . Bile ducts are straight and taper abruptly toward the periphery. The dilated bile ducts are within central one-half of the liever for the porta hepatis.

tortuosity of ducts (“proportional" dilatation. Fig.

4. 5). When there was disagreement in the

diagnosis. they were asked to discuss and agree

to diagnose one disease .

RESULTS

a b

Jae Hoon Li m, et al : CT Characterization of 8ile Duct D i l~tation

Fig. 2. Central dilatation in a 45-year-old woman with recurrent pyogenic cholangitis. Cholangiogram shows dilatation of the extrahepatic bile ducts and larger intrahepatic bile ducts but peripher려 bile ducts are not dilated at all. Dilated intrahepatic bile ducts are rigid. straight and taper abrup t1y toward the periphery ‘ Note numerous “lling defects of stones in the extrahepatic ducts .

Only using the CT pattern of bile duct dilata­

tion , the three observers correctly classified 42 of

the 62 cases (68%). In 15 cases in which observers

initially disagreed but agreed after discussion ,

their classification was correct in 12 cases and in­

correct in three cases. In the remaining five cases,

all observers agreed but classification was incor-

Fig. 3. Peripheral dilatation in a 52-year-old man with clonorchiasis. (a) CT scan shows diffuse uniform dilatation of the intrahepatic ducts. predominantly in the periphery of the liver. The central ducts are also dilated but minimally dilated. (b) Endoscopic retrograde cholangiogram shows diffuse dilatation ofthe small and medium sized intrahepatic bile ducts in the left hepatic lobe . Note more severe dilatation at the periphery of the liver. The left h epatic duct and extrahepatic ducts are minimally dilated.

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Journal of Korean Radi이ogical Society 1992 ; 28(4):601"'608

a b

Fig. 4. Proportional dilatation in a 72-year-old woman with carcinoma of the head of ,the pancreas. (a) CT scan shows dilatation of the large and small intrahepatic bile ducts. The larger bile ducts are dilated more severely than the smaller bile ducts. Note slight tortuosity and gradual tapering ofthe dilated bile ducts. (b) Percutaneous transhepatic cholangiogram (through a catheter) shows severe dilatation ofthe extrahepatic ducts (EHD) and larger intrahepatic ducts and gradual tapering toward the periphery. Note tortuosity of the intrahepatic bile ducts

rect. Thus three radiologists together made cor­

rect diagnosis in 54 of the 62 cases (87%) and

incorrect diagnosis in eight cases (13%).

Regarding individua1 disease. observers correct­

ly classified ten ofthe 14 patients with RPC(71 %).

17 ofthe 18 patients with clonorchiasis (94%). 와ld

27 ofthe 30 patients with carcinoma along the ex­

trahepatic ducts(90%).

Observers misclassified four cases of RPC: three

cases were misinterpreted as carcinomas (Fig. 6)

and one case as clonorchiasis. Three carcinomas

were misclassified as RPC in two cases (Fig. 7) 없ld

clonorchiasis in one case. One case of clonorchiasis

was misclassified as carcinoma(Fig. 8).

DISCUSSION

Pattern of biliary dilatation in each bile duct

disease is different from the others; for example.

in Caroli disease. intrahepatic cystic biliary dilata­

tion is quite characteristic; in sclerosing

cholangitis. biliary tree is tortuous. focally dilated.

naπow and discontinuous; in choledocha1 cyst. ex­

trahepatic ducts are cystically dilated. More com-

Fig.5. Proportional dilatation in a 67-year-old man with carcinoma of the ampulla ofVater. The right and left hepatic ducts. segmental and subsegmental bile ducts are dilated a :ld taper gradually toward the periphery. Far peripheral ducts are not dilated. Note slight tortuosity of the dilated ducts.

mon diseases. especially in orienta1 countries such

as RPC. clonorchiasis and cancer along the bile

ducts genera1ly cause the characteristic pattern of

biliary dilatation.

In RPC. the extrahepatic bile ducts and the

larger (“central") intrahepatic ducts. such as the

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Fig. 6. Proportional dilatation caused by recurrent pyogenic cholangitis in a 72-year-old man. Three observers classified as proportional dilatation and diagnosed as carcinoma.

Fig.7. Central dilatation caused by carcinoma ofthe ampulla of Vater in a 54-year-old man. Three observers classified as central dilatation and diagnos­ed as recurrent pyogenic cholangitis.

right and left hepatic ducts and its first tributaries

are dilated while small tributaries are not dilated

(4-7) (Fig. 1. 2). The dilated 1arger intrahepatic

ducts taper abruptly and straight as one goes to

the periphery of the liver, resulting in an “ ar­

rowhead' ’ configuration toward the periphery of

the liver (7). This pattem ofbiliary dilatation is due

probab1y to 10ss of e1asticity of the 1arger bile ducts

by recurrent infection. and in f1ammationlfibrosis

of the small intrahepatic bile ducts.

Jae Hoon Li m, et al : CT Characterization of Bile uuct Dilatation

Fig. 8. Proportional dilatation caused by clonor­chiasis in a 56-year-old man. Three observers classified as proportional dilatation and diagnosed as carcinoma.

In clonorchiasis, the small (“peripheral") or

meduim-sized intrahepatic bile ducts are dilated

diffuse1y , while the 1arge intrahepatic ducts and

extrahepatic bile ducts are norma1 or slightly

dilated(8-12) (Fig. 3). Dilatation of the smaller bile

ducts is cased by the f1uke itself as the f1ukes reside

in the smaller intrahepatic ducts and causes

mechanical obstruction , adenomatous

hyperp1asia ofthe bile ducts, mucus hyperproduc­

tion and periducta1 fibrosis (8-10). Extrahepatic

duct involvement is generally uncommon.

In cancer of the bile duct such as cho1angiocar­

cinoma, carcinoma of the pancreas and ampulla

ofVater, the entire bile ducts proximal to the mass

are dilated “ proportional1y" regard1ess of the level

of obstruction (Fig. 4 , 5). though the severity of

dilatation depends upon the degree and duration

of obstruction. In moderate to severe dilatation ,

biliary tree becomes tortuous. Fig. 8 illustrates the

characteristic pattem of bile duct dilatation in pa­

tients with RPC , clonorchiasis and carcinoma.

CT is very sensitive in the delineation of the

dilated biliary tree(CT characterization) and deter­

mination of the level of obstruction. However ,

delineation of the causes of biliary obstruction is

sometimes difficult or impossible. Some stones in

the bile ducts are not visualized as attenuation of

stones is similar to bile or adjacent liver paren-

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Journal of Korean Radi이ogical Society 1992 ; 28(4):601"'608

b

c Fig. 9. Schematic drawing of characteristic bile duct dilatation. a . Central dilatation in patients with recurrent pyogenic cholangitis. Note straightening, abrupt peripheral tapering decreased arborization and ob­tuse angle of branching. b. Peripheral dilatation in patients with clonorchiasis. Note normal extrahepatic ducts. and ‘too many ’

dilated peripheral intrahepatic bile ducts. c. Proportional dilatation in patients with carcinoma. Note tortuosity of the dilated intrahepatic bile ducts.

chyma(7). Flukes in the small intrahepatic bile

ducts are too small to be seen (12). Carcinoma of

the bile duct or pancreas could be well delineated

in general. but sometimes when a mass is sm외1 ，

its delineation is difficult(2.3). In our 62 cases.

primary pathology was depicted on CT in 30 cases

(48%) and equivoc외 in five cases (8%): in 27 cases

(44%). the cause of obstruction was not depicted.

The low rate of depiction of primary cause of

obstruction is because of relatively large propor­

tion of clonorchiasis. CT is particularly insensitive

in depicting f1ukes: aggregates of f1ukes were

demonstrated in only two of the 18 cases (11 %)

of clonorchiasis. In RPC , stone was demonstrated

in nine ofthe 14 cases (64%) and equivocal in one

case. In the 30 carcinomas. mass was

demonstrated in 19 cases (63%) and equivocal in

four cases.

Clinical significance of CT characterization of

bile duct dilatation is its usefulness in patients

whose CT discloses only biliary dilatation with no

evident primary pathology. For example. the

primary pathology was demonstrated in only 11 %

in clonorchiasis but correct diagnosis could be

made in 94% on the basis ofCT characterization.

In four ofthe 14 cases ofRPC (29%). the stone was

not demonstrated. In seven of the 30 car­

cinomas(23%) along the bile ducts. the cancer

mass was not demonstrated in CT: the masses

were too small or incorporated with the adjacent

organ or the pancreas and only abrupt obstruction

of the bile duct was demonstrated. In these CT

scans, the cause of bile duct obstruction could be

suggested only on the basis of CT cholangiogram

and further appropriate procedure could be

tailored . When RPC is suggested on the basis of

CT characterization. endoscopic retrograde

cholangiography is indicated as a next step for

diagnosis as well as a “ road map" for a surgeon.

When clonorchiasis is suggested, stool test for ova

of Clonorchis sinensis is indicated: endoscopic

retrograde cholangiography or percutaneous tran­

shepatic cholangiography is too invasive for these

patients. When carcinoma is suggested. en­

doscopic retrograde cholangiography or per-

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cutaneous transhepatic cholangiography and/or

percutaneous transhepatic biliary drainage is con­

sidered as a next procedure.

The study is somewhat artificial and not in a

real clinical setting in that only three common

diseases were included and interpreters were to

consider only three diseases and to pick the most

likely ofthe three. In clinical setting. by contract

a radiologist is faced with considering many other

diagnostic possibilities including sclerosing

cholangitis. Caroli disease and choledochal cyst.

In our country. however. other biliary tract

diseases other than the three common diseases.

such as sclerosing cholangitis are rare. Caroli

disease and choledochal cyst are very easy to

diagnose as the biliary dilatation is quite

characteristic. Another problem. which are tried

to avoid. is that these three diseases are inter­

related. that is two or three diseases may be pre­

sent simultaneously. or one disease may cause

another diseases as clonorchiasis may be the cases

ofrecurrent pyogenic cholangitis or carcinoma of

the bile ducts (11-13) . The other point is in patients

with RPC with localised dilatation of the in­

trahepatic bile ducts. such as the lateral segment

of the left hepatic lobe or posterior segment of the

right hepatic lobe. caused by stricture: in these pa­

tients. the intrahepatic bile ducts are dilated

sometimes up to the periphery .

Authors thank Hye Young Lee for her help in

the illustrations of this manuscrip t.

Jae Hoon Li m, et al : CT Characterization of Bile Duct Dilatation

160:43-47

3. Baron RL , Stanley RJ , LeeJKY , etal. Aprospec­

tive comparison ofbiliary obstruction using com­

puted tomography and ultrasonography.

Radiology 1982: 145:91-98

4. Wastie ML. Cunningham IGE. Roentgenologic

findings in recurrent pyogenic cholangitis. AJR

1973;119:71-77

5 . Lam SK. Wong KP , Chan PKW. Ngan H, Ong GB.

Recurrent pyogenic cholangitis: a study by en­

doscopic retrograde cholangiography. Gastro­

enterology 1978:74:1196-1203

6. Chau EMT. Leong LLY , Chan FL. Recurrent

pyogenic cholangitis: u1trasound evaluation

compared with endoscopic retrograde

cholangiopancreatography. Clin Radiol 1987:

38:79-85

7. Chan F-L , Man S-W , Leong LLY. Fan S-T.

Evaluation of recurrent pyogenic cholangitis

withCT ‘ analysis of 50 patients. Radiology 1989;

170:165-169

8 . Okuda K, Emura T . Morokuma K, Kojima S ,

Yokagawa M. Clonorchiasis studied by per­

cutaneous cholangiography and a therapeutic

trial of toluene-2 , 4-diiso-thiocyanate.

Gastroenterology 1973:65:457-461

9. Choi TK. Wong KP. Wong J. Cholangiographic

appearance in clonorchiasis. Br J Radiol 1984;

57:681-684

10. Lim JH , Ko YT. Lee DH. Kim SY. Clonorchiasis:

sonographic findings in 59 proved cases. AJR

1989;152;761-764

11. Choi BI. Park JH. Kim YI. et a l. Peripheral

REFERENCES cholangiocarcinoma and clonorchiasis: CT fin­

dings. Radiology 1984;169:149-153

1. Laing FC. Jeffrey RB Jr. Wing VW. Nyberg DA. 12. Choi BI. Kim HJ. Han MC . Do YS , Han MH. Lee

Biliary dilatation: defining the level and cause by SH. CT findings of clonorchiasis. AJR 1989;

real-time US. Radiology 1986 ‘ 160:39-42 152:281-284

2. Gibson RN . Yeung E. Thompson JN. et a l. Bile 13. Lim JH. Oriental cholangiohepatitis: pathologic.

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cause. and tumorresectability. Radiology 1986: 157:1-8

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Journal of Korean Radiological Society 1992 ; 28(4):601-608

〈국문 요약〉

CT에 나타난 담관확장의 특징 : 폐쇄성황달의 감별진단

경희대학교 의과대학 진단방사선과학교실

임재훈·윤 엽·고영태·이동호·양 익

우리나라에 흔한 3가지 담도질환， 즉 재발성화농담관염， 간홈충증과 담관암은 각각 특정적인 담관확장을 초래하는

데， 재발성화농담관염은 중심담관의 확장， 간홉충증은 말초담관의 확장， 그리고 담관암은 전반적인 담관확장을 초래

한다. 저자들은 전산화단충촬영상에서 담관 결석이나 종괴등의 질병자체가 보이지 않는 경우 전산화단충상에 나타난

담관확장의 유형만으로 판단하여 얼마나 이들 병을 진단할 수 있는가를 검토 하였다.

화농담관염 14예， 간홉충증 18예와 담관암 30예의 전산화 단충촬영상을 섞어 3명의 방사선과 전문의에게 주고

CT에 나타난 담관폐쇄의 유형만으로 3가지 병을 진단하게 하였다.

전체 62명중 54명 (87%) 에서 담관확장의 유형만으로 진단이 가능하여 재발성화농담관염， 간홉충증 및 담관암에서

전산화단충촬영에 나타난 담관확장의 특정은 폐쇄성황달의 진단에 매우 유용하고， 특히 질병자체가 잘 나타나지 않

는 예에서 유용하게 이용할 수 있다고 믿는다.

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